Malacoplakia of the kidney: apparent improvement following medical management.

Malacoplakia of the kidney is a rare histopathologic entity of unknown etiology. Patients may present with a renal mass or with urinary tract infection. The prognosis has been uniformly poor excepting in those patients with unilateral involvement treated by nephrectomy. A 31 year old woman presented with acute renal failure and pyelonephritis. Renal biopsy revealed an interstitial infiltrate of large histiocytic cells with intracytoplasmic PAS-positive granules and calcospherules, findings consistent with malacoplakia. Following antibiotic treatment and dialysis, the patient has had a gradual improvement in renal function.